Is the 1mg-dexamethasone suppression test a precise marker of glucocorticoid excess and cardiometabolic risk in patients with adrenal incidentalomas?

Aim To analyze if the 1mg-dexamethasone suppression test (DST) is a reliable marker of glucocorticoid excess and cardiometabolic risk in patients with adrenal incidentalomas (AIs). Methods Cross-sectional study of patients with nonfunctioning adrenal incidentalomas (NFAIs, defined by cortisol post-DST ≤ 1.8 µg/dL) and patients with autonomous cortisol secretion (ACS, defined by cortisol post-DST > 1.8 µg/Dl). The urinary steroid profile (USP) was determined by gas chromatography coupled to mass spectrometry. Both groups were matched by sex, age and body mass index. Results Forty-nine patients with AIs (25 with ACS and 24 with NFAI) were included. As a whole, AIs showed a high excretion of β-cortolone, tetrahydro-11-deoxycortisol (THS), α-cortolone, α-cortol, tetrahydrocortisol (THF) and tetrahydrocortisone (THE). A positive yet modest correlation between post-DST cortisol and total excretion of glucocorticoid metabolites ( r = 0.401, P = 0.004) was observed, with the stronger being observed with total THS ( r = 0.548, P < 0.001) and THF ( r = 0.441, P = 0.002). Some of the metabolites that were elevated in patients with AIs, were higher in patients with ACS-related comorbidities than in those without comorbidities. Post-DST cortisol showed a fair diagnostic accuracy for the prediction of ACS-related comorbidities (AUC 0.767 [95% CI 0.634–0.882]). However, post-DST diagnostic accuracy improved when combined with urinary cortisone, α-cortol, THS and serum DHEAS (0.853 [0.712‒0.954]). Conclusion The DST has a positive, but modest, correlation with urinary glucocorticoid excretion. Similarly, the diagnostic accuracy of the DST for the prediction of ACS-related comorbidities is only fair, but it may be improved if combined with the results of the USP and serum DHEAS. Significance statement This is the first study aimed to evaluate if 1mg-dexamethasone suppression test (DST) is a reliable marker of glucocorticoid excess and cardiometabolic risk in patients with adrenal incidentalomas (AIs) and if urinary steroid profile was measured by GS-MS could improve such a prediction. We found a positive yet modest correlation between post-DST cortisol and total excretion of glucocorticoid metabolites, with the stronger being observed with total tetrahydro-11-deoxycortisol (THS) and tetrahydrocortisol. Post-DST cortisol showed a fair diagnostic accuracy for the prediction of ACS-related comorbidities (AUC 0.767). However, post-DST diagnostic accuracy improved when combined with urinary cortisone, α-cortol, THS and serum DHEAS (0.853).